High-Compaction Spherical Carbon with Tunable Rich Pore Structures for Efficient Sodium Storage

Hard carbon, owing to its tunable pore structure, is emerges as a promising anode material for sodium-ion batteries (SIBs) and holds a great potential to improve low-potential plateau capacity  for boosting the energy density of full cells. However, a key challenge for large-scale SIBs applications is the trade-off between increasing sodium storage pore volume and maintaining high compaction density. Herein, a pre-pore engineering strategy is employed to fabricate high-compaction-density spherical hard carbon with tunable pore structures, realizing simultaneous enhancement of gravimetric and volumetric capacities. Importantly, it is found that pore structure regulation profoundly affects performance across multiple scales. Microscopically, adjusting pore structure alters intrinsic electrochemical properties, with a reversible capacity of 375.40 mAh g^-1 and initial Coulombic efficiency of 90.1%. At the mesoscale, monodisperse spheres reduce packing voids and improve compaction. As a result, even under high compaction, the anode maintains a high reversible capacity of 359.49 mAh g^-1 and exhibits an excellent volumetric capacity of 390.30 mAh cm^-3. The assembly of an Ah-level pouch cell further demonstrates its practical potential. In addition, fabrication methods determine electrode structure and sodium storage at the macroscopic scale, leading to clear differences in low-potential intercalation and pore-filling behaviors between lab-made and practical electrodes.